Scientists have used state-of-the-art technology to evolve gel-based carriers known as nanogels that carry pheromones to repel pests Consignments
of Indian fruit and vegetables often face quarantine restrictions or rejections in export markets because of pest infestation or high pesticide residues. In the domestic market, too, unsafe levels of pesticide residues in food items have become a major concern, inviting injunctions from courts to curb this menace. The solution lies in finding and promoting safer, preferably non-toxic means of pest control. Options for implementing this include the use of bio-pesticides or natural enemies (predators) of the pests; hot and cold treatment and irradiation of the produce; and equipping plants with inbuilt resistance against pests and diseases through genetic modification, among others. However, most of these methods have their own limitations that restrict their usage.
Another hi-tech, yet easy-to-use method that has shown good potential for controlling pests is the deployment of pheromones - natural or artificial odours, including sex aromas - that lure insects to either trap and destroy them or disrupt their breeding. These aromas, similar to the ones emitted by insects themselves, are species-specific. They, therefore, do not result in killing all insects indiscriminately - as is done by most pesticides - regardless of whether they are harmful or useful to the crops as pollinators or predators of pests. Besides, these are required to be used in extremely low doses and do not leave any harmful residue that affects the marketability of the produce. In the past half century, scientists have identified and synthesised around 1,500 pheromones for different insect species. These have found widespread application in agriculture, forestry and urban pest management.
However, for using pheromones on a mass scale, the techniques for dispensing them in fields need to be reliable, economical and simple enough for the farmers to use. For this, many methods, including aerial spraying, have been tried out but with limited success. Many medium (carrier)-based pheromone dispensers have also been developed and are commercially available. But most of them are sensitive to ambient temperature and other atmospheric conditions that limit their use to certain seasons only. In recent years, various kinds of gels have been used as the medium or carrier for pheromones for field application. However, many of the commonly used gels, notably hydrogel, swell or shrink, depending on the obtaining humidity level, or tend to degenerate under other adverse circumstances.
To get over these constraints, scientists have now used state-of-the-art nanotechnology to evolve hassle-free gel-based carriers for pheromones called nanogels. They have been found to be the most convenient option for field application of pheromones in all seasons, regardless of the temperature or humidity. Besides, they are easy to transport and do not require specialised storage. Pheromones absorbed in nanogels are released slowly over an extended period to provide longer-term protection against pests. Nanogels are now also used in human and animal health care for slow delivery of drugs in the required quantity to targeted spots in the body. In pest control, too, pheromone-doped nanogels have displayed the ability to release pheromones gradually in the needed quantity.
The technology for preparing these nanogels for agricultural use has been evolved by a team of scientists belonging to the Bengaluru-based Indian Institute of Science and the National Bureau of Agricultural Insect Resources (NBAIR) of the Indian Council of Agricultural Research. "This simple, practical and low-cost environment-friendly method of pest management has a significant potential for crop protection due to its long-lasting beneficial activity, excellent efficacy and favourable safety profile", says NBAIR senior scientist Deepa Bhagat, who was part of the team that invented the nanogel. This technology can be efficiently and economically carried forward from the research laboratory to agricultural fields to control pests of crops such as cotton, pigeon pea, chickpea, tomato, brinjal, coffee, guava, mango, rice and others, Bhagat points out. The developers of the nanogel have already initiated the patent process before it is licensed to entrepreneurs for commercial production and promotion.